This application claims priority to an application entitled xe2x80x9cDevice for Aligning Optical Source and Optical Fiber in Optical Source Modulexe2x80x9d filed with the Korean Industrial Property Office on Aug. 1, 2000 and there duly assigned Ser. No. 2000-44531.
1. Field of the Invention
The present invention relates generally to an optical source module and, in particular, to a device for aligning an optical source and an optical fiber in the optical source module.
2. Description of the Related Art
In general, the function of an optical source module is essential in all aspects of transmitting and receiving an optical signal in an optical communications system. Namely, an optical source module is typically used as a pump laser diode module, semiconductor optical-amplifier module, and for transmitting/receiving module in the range of 155 Mbit and 2.5 Gbit.
FIG. 1a is a top view illustrating the construction of a conventional optical source module. FIG. 1b is a side view illustrating the construction of the conventional optical source module. As shown in FIGS. 1a and 1b, the conventional optical source module 100 comprises a housing 110, a substrate 120, a laser diode 130, a photo diode 140, an optical fiber 150, an optical ferrule 160, a saddle 170, a thermoelectric cooler 180, a thermister 190, and, a window ferrule 162.
According to the conventional optical source module 100 with the above construction, the laser diode 130 and an optical fiber 150 are aligned according to the following steps. First, the laser diode 130 is mounted on the substrate 120. Then, the optical fiber 150 and the optical ferrule 160 are soldered together, and the lower portion of the saddle 170 is mounted on the substrate 120. Thereafter, when electric power is supplied to the laser diode 130 to emit light, the position of the optical ferrule 160 is adjusted to realize a maximum light-receiving position. Once the maximum light-receiving position is determined, the saddle 170 and the optical ferrule 160 are welded together. Here, the thermal distortion caused by this welding process should be within an alignment allowable error range.
In order to obtain a higher optical coupling efficiency between the optical fiber and the laser diode, a lens having the same shape as archenterons of the laser diode is processed at one end of the optical fiber for a precise alignment in six axes. Here, the error range of an axis should be within the least allowable error range, which is preferably less than 0.2 xcexcm.
FIG. 2a is a side view illustrating a device for aligning an optical source and an optical fiber according to a first embodiment of the conventional art. FIG. 2b is a front view of the device in FIG. 2a. FIG. 3 is a side view magnifying an optical ferrule and saddles of the device in FIG. 2a. FIG. 4 is a side view magnifying an optical ferrule and saddles of the device in accordance with a second embodiment of the conventional art.
Referring to FIGS. 2a to 4, the saddles 170 and 270 of the device for aligning the optical source and the optical fiber according to the first and second embodiments of the conventional art are thermally distorted to a degree of 5 to 20 xcexcm in an y-axis (vertical) direction due to the heat applied to the respective welded sections S. Once the heat is applied to the welded sections S, the heat is conducted toward the arrow direction, as shown in FIGS. 3 and 4. Also, as the optical ferrule 160 including the optical fiber 150 is displaced downward in a vertical direction, the vertically-downward displacement of the optical ferrule 160 decreases optical coupling efficiency between the optical source and the optical fiber, thereby impeding reliability of the optical source module.
FIG. 5a is the side view of a device for aligning an optical source and an optical fiber according to a third embodiment of the conventional art. FIG. 5b is a view illustrating the cross section line B-Bxe2x80x2 in FIG. 5a. FIG. 6a is a side view of the device for aligning an optical source and an optical fiber according to a forth embodiment of the conventional art. FIG. 6b is a view illustrating the cross section line A-Axe2x80x2 in FIG. 6a. FIG. 7 is a graph illustrating the thermal distortion of the device according to the third and forth embodiments of the conventional art. Here, the horizontal axis represents time, while the vertical axis represents the degree of thermal distortion, respectively.
Referring to FIGS. 5a to 6b, the saddles 370 and 470 of the device according to the third and forth embodiments of the conventional art includes arms 372 and 473 formed with distance from bases 371 and 471, respectively. In this prior art system, the saddles 370 and 470 exhibit a relatively small value of 0.4 xcexcm in thermal distortion in the y-axis direction as shown in FIG. 7.
However, the degree of thermal distortion is greater than the allowable error range, which should be less than 0.2 xcexcm for thermal distortion in the vertical direction for optimal performance. In order to obtain an optimal error range, the optical ferrule 160 is frequently removed using a gripper to re-align the optical ferrule 160, and such an operation is a time-consuming process and cumbersome during the manufacturing process. Moreover, a residual stress which occurs during the fabrication process should be minimized to enhance the durability of the optical source module. Thus, it is apparent that a need exists for improved techniques for packaging optical modules, such that internal fiber connections can be utilized without increased manufacturing cost, decreased reliability and other problems associated with a conventional optical source module.
The present invention is directed to a device for aligning an optical source and an optical fiber in an optical source module to minimize a thermal distortion and residual stress caused by the welding of the optical fiber ferrule and the saddle member.
The present invention is related to a device for aligning an optical source and an optical fiber in an optical source module to maintain a higher optical coupling efficiency without re-alignment after the first alignment attempt between the optical source and the optical fiber.
Accordingly, the present invention provides a device capable of aligning an optical source and an optical fiber in an optical source module, which includes a substrate for mounting the optical source, an optical fiber ferrule for supporting the optical fiber so that the optical fiber can receive light emitted from the optical source, and a saddle mounted on the substrate near the optical source for supporting the optical fiber ferrule. The saddle includes a pair of base layers spaced a part by a predetermined distance; a sub-rib member near extending upwardly from the inner end, adjacent to the optical fiber ferrule, of the respective base layer; a center-rib member having a smaller width than the sub-rib layer extending upwardly from the center portion of the respective sub-rib layer; an arm member having a greater width than the center rib extending upwardly from the top of the respective center-rib member, the respective arm member having a pair of welded area positioned at both ends for coupling the optical fiber ferrule along a longitudinal direction of the optical fiber ferrule; a reinforcing member having tapered ends extending upwardly from the top portion of the respective arm member; and, a loop member for coupling the top end of the respective reinforcing member together.